Until recently it was rather difficult to accurately detect leaks in operating, pressurized closed-loop systems (e.g., air conditioning and refrigeration systems). Often a serviceman or technician was required to interpret test results which were very vague and ambiguous. One method typically used was to employ a Halide torch. This method required the serviceman or technician to observe a particular color change when escaping system chloroflourocarbon refrigerant material (e.g., FREON.RTM.) came in contact with the torch flame. Other methods for leak detection employs the use of soap bubbles and/or electronic detectors.
Yet another method of leak detection employs the use of fluorescent leak detection compositions. Here a fluorescent leak detection composition is applied to the outer surface of a system's equipment or pipes. A composition which is suitable for this latter approach is disclosed in U.S. Pat. No. 4,249,412.
Not only were the test results of the aforementioned methods difficult to interpret, but also they often did not pinpoint the exact location of the leak or locate multiple leaks. In practice, the serviceman or technician would have difficulty showing a customer the exact location of the leak or leaks. In many cases, the serviceman was more apt to recharge the system with additional refrigerant rather than locating and repairing the existing leak.
In more recent years, it has become common practice in the automotive air conditioning field to provide one pound cans of a pre-mixed formulation of a refrigerant and a leak detection composition (e.g., a fluorescent dye and a lubrication oil) to be infused into an operating, pressurized closed-loop system. This practice allows system leaks to be reliably pinpointed when the refrigerant and fluorescent dye formulation is used in conjunction with an ultraviolet light.
Specifically, since the operating closed-loop system is under pressure, the fluorescent dye is forced outwardly through any existing holes, cracks and/or loose connections or fittings in the system; thereby, becoming clearly visible and highlighted to the human eye when subjected to the ultraviolet light source. One example of a method and apparatus especially suitable for the aforementioned pre-mixed formulation system is disclosed in the trade literature entitled "Spectroline.RTM.Automotive Leak Detection Systems", available from Spectronics Corporation, of Westbury, N.Y.
Although the use of one pound cans was very common, in the past few years, many companies have since ceased to manufacture and/or distribute this product. One of the main reasons for the trend towards terminating the manufacturer and distribution of such one pound cans stems from the discovery that the refrigerant contained therein (i.e., chlorofluorocarbons) aid in destroying the earth's ozone layer.
Notwithstanding the above, there are still many definite advantages associated with employing infused pre-mixed refrigerant/leak detection compositions for locating leaks in an operating, pressurized close-loop system. Some advantages of infusing a pre-mixed refrigerant/leak detection formulation, instead of relying on the aforementioned methods (e.g., use of halide torches, soap bubbles and/or electronic detectors), include: (1) being able to accurately pinpoint the exact source of the leak or leaks; (2) being able to positively recognize the leak without having to interpret the test results; (3) being able to directly show a customer the existing leak or leaks; and (4) making it practical for the leaks to be repaired rather than just refilling the system with additional refrigerant.
The importance of being able to detect and repair such leaks is two-fold. First, the efficiency of the system is reestablished following the necessary repairs. This conserves energy. Secondly, the amount of refrigerant escaping into the atmosphere is minimized; thereby, minimizing the depletion of the earth's ozone layer.
However, as stated earlier, although pre-mixed one pound cans containing a refrigerant and a leak detection composition performed satisfactorily, for the most part, such one pound cans are no longer being sold. Moreover, as also stated earlier, it is impractical, if not impossible, to neatly and efficiently charge large commercial air conditioning and refrigeration systems with the existing pre-mixed one pound can formulations.
When infusing a system with a pre-mixed leak detection formulation, it is most desirable to charge the system with as little carrier refrigerant as possible until the leak or leaks are located, since the refrigerant is often vented to the atmosphere when repairing the leak. However, if the refrigerant is not vented, it is often pumped from the system to an external storage tank to be re-used after the leak(s) has been repaired.
The use of pre-mixed cylinders of the refrigerant and leak detection composition formulations afford only a minimal degree of flexibility in controlling the amount of the leak detection composition to be added to a particular system. In large commercial air conditioning and refrigeration systems, the amount and concentration of the leak detection composition necessary to check for leaks will vary depending on the weight of the refrigerant charge and the oil charge of that system.
By employing the aforementioned prior art practices, nearly all systems will be either undercharged or overcharged as a result of the use of the pre-mixed cylinder formulations. Accordingly, if a serviceman or technician is to effectively detect leaks in a large commercial system, various quantities of a leak detection composition, in various concentrations, must be repeatedly infused into the system.
As mentioned above, improperly charging a system is highly undesirable since it has the potential of resulting in the following problems: (a) it can cause the escaping leak detection composition to be spilled onto the system equipment; (b) it can cause excess refrigerant to be vented to the atmosphere; and, (c) it can cause an improper ratio of lubrication oil to refrigerant to leak detection composition to be present in the system. This latter problem can be fatal to the closed-loop system due to there being an insufficient amount of oil present to lubricate the system and/or there being an insufficient amount of the fluorescent dye present which will result in a greatly reduced fluorescent effect of the leak detection composition.
Additionally, commercial air conditioning and refrigeration systems use not only various amounts of refrigerant but also various types of refrigerants. Examples of commercially useful refrigerants include: R-11, R-12, R-22, R-502, R-500, R-114, R-113, R-23, R-13, and R-503. The various types of refrigerants used preclude the practical stocking and supply of the correct concentrations and amounts of leak detection formulations necessary for every particular commercial system. Moreover, many types of dyes, such as DuPont's Dytel Red Visible Dye, manufactured by the E.I. DuPont de Nemours & Co. of Wilmington, Del., are normally only stocked by distributors in pre-mixed refrigerant/dye formulations containing R-12 and R-22 refrigerants.
Although they are highly effective in locating leaks within a closed-loop system, it should also be noted that the usefulness of visible dyes has diminished due to the improper use and control of such compositions. For example, since the amount of visible dye additions to closed-loop systems has not been controlled for various reasons, this often resulted with grossly overcharging the system being checked. Overcharging is highly undesirable, especially when fluorescent dyes are employed, since the fluorescent response of such dyes can be quenched if present in high concentrations.
The apparatus and method disclosed in U.S. Pat. No. 4,938,063 overcame many of the foregoing deficiencies by providing an apparatus and method for neatly and efficiently infusing a mixture comprising a leak detection composition and a system carrier fluid into an operating, pressurized closed-loop system for the purpose of detecting and pinpointing leaks. The invention disclosed in U.S. Pat. No. 4,938,063 accomplished this result in a manner which minimized the venting of system carrier fluid to the atmosphere, while providing a system carrier fluid and leak detection material mixture which was appropriate for a particular sized commercial system.
The apparatus disclosed in U.S. Pat. No. 4,938,063 comprises, among other things, a refillable sealed reservoir designed to hold a predetermined amount and concentration of a liquid material. If the apparatus is used for detecting leaks in an operating, pressurized closed-loop system, the liquid material comprises a leak detection composition.
When practicing the invention disclosed in U.S. Pat. No. 4,938,063, if, for example, the system being tested for leaks requires two ounces of a specific leak detection composition, and if the sealed, refillable, reservoir capacity is only one ounce, the serviceman or technician testing the system would generally perform the following steps: (a) fill the sealed, refillable, reservoir with a first one ounce supply of the desired leak detection composition in accordance with the process disclosed therein, (b) connect the sealed reservoir to the closed-loop system being tested, (c) discharge the contents of the reservoir into the system, (d) refill the reservoir with a second one ounce supply of the same leak detection composition, and (e) discharge the contents of the refilled reservoir into the system.
The aforementioned method is especially useful when using the refillable sealed reservoir to repeatedly discharge the same leak detection composition into the same closed-loop system. However, as stated earlier, there are many different types of refrigerants presently being employed. Since each refrigerant is miscible with only a limited group of compositions, when testing for leaks, it is imperative to employ a leak detection composition which is compatible therewith.
Specifically, in the air conditioning and refrigeration industry, chloroflourocarbon (CFC) compounds, such as dichlorodifluoromethane, have been used extensively for many years as refrigerants. Dichlorodifluoromethane, commonly referred to in the industry as "R-12", is the refrigerant of choice for many air conditioning systems such as automobile air conditioners.
However, it has recently been determined that, when CFC compounds are released to the atmosphere, they have the potential of damaging the earth's ozone layer. Consequently, the industry has sought to find a non-CFC substitute for such CFC refrigerants.
In response to this need, it has been discovered that hydrofluorocarbon (HFC) compounds can be used as refrigerants without having the adverse effects on the earth's ozone layer as do their CFC counterparts. One of the HFC compounds which the refrigeration and air conditioning industry has identified as a suitable substitute for CFC compound R-12 is 1,1,1,2-tetrafluoroethane, commonly referred to as "R-134a".
Although R-134a does not have any known deleterious effects on the earth's ozone layer, the industry noted that it is not a "drop-in" substitute for R-12 refrigerants. Specifically, conventional refrigeration systems which employ R-12 as the refrigerant generally use mineral oils to lubricate their compressor. This does not create a problem in such conventional systems since R-12 is completely miscible with mineral oils throughout the entire range of refrigeration system temperatures.
On the other hand, conventional refrigeration lubricants such as mineral oil cannot be employed with HFC compositions such as R-134a, since R-134a is not miscible with mineral oils. Consequently, if R-134a is employed in a refrigeration system it cannot come into contact with any mineral oil since doing so would create a serious problem. Specifically, since HFC compounds are immiscible with mineral oils, the blending of the two will not produce a homogeneous mixture. This will, in turn, contaminate and possibly damage the refrigeration system.
Moreover, one of the lubricants of choice for systems which employ R-134a is polyalkylene glycol (PAG). While PAG is very compatible with R-134a refrigerant, it cannot be used where there is a possibility of cross-contamination with systems which employ mineral oil as the lubricant (i.e., CFC-based systems). For example, the PAG will react with chloride remaining in the residual oil, or present as a residual in the supply tubes, hoses, mist infuser, etc. This reaction with the chloride ions will form a sludge which can be extremely harmful to the operation of the closed-loop system being checked.
Regardless of whether the refrigerant employed is a CFC compound or an HFC compound, it will always be necessary to detect the presence of leaks since air conditioning and refrigeration systems are pressurized "closed-loop" systems. If a single, sealed, refillable reservoir, similar to that disclosed in U.S. Pat. No. 4,938,063, is employed as part of an apparatus to detect leaks in both CFC-based and HFC-based closed-loop systems, a serious problem can occur due to the cross-contamination potential set out above.
There are many different types of CFC and HFC refrigeration compounds. Each compound has specific compositions with which it can be mixed. Therefore, in order to avoid the problems associated with cross-contamination, the user of an apparatus employing the sealed, refillable reservoir disclosed in U.S. Pat. No. 4,938,063 must either: (a) possess a large number of sealed, refillable reservoirs, each designated for employment with a specific refrigerant, or (b) thoroughly clean the sealed, refillable reservoir and connecting hoses after each use to remove all traces of a composition which may be incompatible with the system refrigerant, the carrier fluid, the leak detection material and/or the refrigeration lubricant.
As can be seen, either approach would be costly and/or time consuming. Therefore, since the trend in the industry is to shift over from CFC-based to HFC-based systems, the air conditioning and refrigeration industry would welcome a means and/or method for detecting leaks in operating, pressurized, closed-loop systems which efficiently and economically resolves the aforementioned problems, especially those associated with cross-contamination.